We know that a lot of things dissolve in water. Let’s do a simple experiment to find out whether the temperature of the water makes a difference to how fast things dissolve in it.
What’s needed:
> Two glasses (preferably identical and tall)
> Cold water
> Hot water (please ask an adult to help you with handling the required things)
> 1-2 liquid food colouring
> Sugar
> Timer
What to do:
Take the two glasses and fill one with cold water and the other with hot water till they are three quarters full. Now take the two different liquid food colouring and drop 1-2 drops of it into both the glasses at the same time. Start your timer. See how long it takes for the food colouring to dissolve.
Does the food colouring dissolve at the same speed in both the glasses?
Next, drop a spoon of sugar into both the glasses. Do not stir. Use your timer to check whether the sugar dissolves faster in one glass than in the other. What have you observed?
The Science behind it:
Everything is made of tiny molecules (which in turn is made of tinier atoms). When the food colouring is dropped into the water, the molecules of food colouring mix into or ‘get between’ the molecules of water till they are completely mixed and can no longer be separated from each other and it is said to have dissolved in water. Water is the solvent (the thing that the colour dissolved in) and the food colouring is the solute (the thing that dissolved in the solvent). The food colouring is mixing with the water owing to a process called diffusion. Diffusion is the movement of particles from an area of high concentration to an area of low concentration, i.e. when we drop a single drop of food colouring on the water, the food colouring is concentrated in that area and it then tries to move to where there is less or no food colouring at all or where the food colouring is at a lower concentration level.
Why the food colouring and sugar dissolved faster in the hot water is because diffusion happens faster in hot water. Molecules move faster in hot water than in cold water and the diffusion of the food colouring molecules from a higher concentration to lower concentration can thus take place faster.
Courtesy: The Science Factory, a scientific enrichment programme for kids.
www.thesciencefactory.in
